Breakthrough Studies on the Plasma Electrolytic Oxidation (PEO) Coating Process

等离子体电解氧化（PEO），也称为微弧氧化（MAO）、火花阳极化和微等离子体氧化，是一种加工技术，其中金属如Al、Mg和Ti的表面被转化成氧化物涂层，厚度范围从几十微米到几百微米。涂层生长通过大量的短暂火花（放电）发生，由局部介电击穿引起。所得涂层可以高度耐磨损和耐腐蚀，并且非常好地粘附到基材上。然而，直到最近，这些等离子体放电的性质，以及这与所得涂层微观结构之间的联系，一直知之甚少。最近在谢菲尔德和剑桥的工作已经产生了关于这些放电的温度、密度、电阻率、空间分布、频率和持续时间的新信息，以及关于这些特性对涂层微观结构的影响的新信息。拟议的项目旨在利用和扩展这项工作中开发的技术，雇用主要负责这些进展的研究人员，并受益于南安普顿经验丰富的等离子体物理学家的投入。目标之一是建立一个新的进程模式。这将定量地了解电路、电解质成分、等离子体放电特性和涂层微观结构之间的相互作用。这应有助于提高工艺的能源效率。通过这种建模提供的增强的理解，然后将被用来探索使用类似PEO的处理来将碳和硼等小原子注入到钢等金属中，从而提高表面硬度的潜力。关于这种可能性的初步报告令人鼓舞。如果它确实被证明是可行的，那么它将在与传统渗碳的竞争中提供主要的节能效益，传统渗碳需要将部件长时间保持在高温下。这项工作将与PEO领域的两家英国中小企业合作开展，因此应能为英国工业带来实质性和相对短期的利益。

Plasma Electrolytic Oxidation (PEO), also known as Micro Arc Oxidation (MAO), Spark Anodising and Microplasma Oxidation, is a processing technique in which the surfaces of metals such as Al, Mg and Ti are converted into oxide coatings, ranging from tens to hundreds of microns in thickness. Coating growth occurs via large numbers of short-lived sparks (electrical discharges), caused by local dielectric breakdown. The resultant coatings can be highly resistant to wear and corrosion, and adhere exceptionally well to the substrate. Until recently, however, the nature of these plasma discharges, and the links between this and the resultant coating microstructure, have been very poorly understood. Recent work at Sheffield and Cambridge has produced new information about the temperature, density, resistivity, spatial distribution, frequency and duration of these discharges, and also about the influence that these characteristics have on the coating microstructure. The proposed project is aimed at utilising and expanding the techniques that have been developed in this work, employing the researchers primarily responsible for these advances, and also benefitting from the input of experienced plasma physicists based in Southampton. One of the objectives will be to create a new process model. This will give quantitative insights into the interplays between electrical circuitry, electrolyte composition, plasma discharge characteristics and coating microstructure. This should assist in the aim of improving the energy efficiency of the process. The enhanced understanding provided by this modelling will then be utilised to explore the potential for using PEO-like processing to implant small atoms, such as carbon and boron, into metals such as steels, giving increased surface hardness. Preliminary reports of this possibility are encouraging. If it does prove to be viable, then it would offer major energy-saving benefits in competition with conventional carburizing, which requires components to be held at high temperatures for extended periods. The work will be carried out in collaboration with two UK SMEs in the PEO field, and should thus lead to substantial and relatively short term benefits to UK industry.